This invention relates generally to electromagnetic fuel injectors of the type used with internal combustion engines. More specifically, it relates to an improvement in a split stream injector.
In an internal combustion engine that has one fuel injector per cylinder, but two intake valves per cylinder, the use of electromagnetic fuel injectors that direct the fuel in separate and distinct paths to each intake valve has been proven to improve the performance and efficiency of the engine. The prior art is represented by U.S. Pat. Nos. 4,657,189 and 4,699,323, both of which are concerned with injectors that direct fuel in two different directions.
The design of the injector of U.S. Pat. No. 4,657,189 is such that the flow is both divided and directed downstream of a metering orifice. A disadvantage of such design is that the flow will not be equally divided if there is misalignment between the metering orifice centerline and the flow splitter/director centerline. For given manufacturing tolerances, such misalignment cannot be avoided in many injectors and therefore it becomes difficult to obtain consistency from injector to injector when the injectors are mass produced.
The injector of U.S. Pat. No. 4,699,323 uses six holes to generate two hollow cones, or plumes. Three of these holes both direct and meter the flow that is used to create one plume while the other three holes do the same for the other plume. If the centerline of the injector is the Z-axis, then the alignment angle of two of the three holes of each set must be controlled in both the X-axis and the Y-axis in order to produce the hollow cone pattern. Moreover, the sizes of the holes must be precisely controlled to attain the desired cone-to-cone distribution. For given manufacturing tolerances in mass production, such controls are difficult to achieve, and therefore mass production consistency from injector to injector is unlikely.
The present invention provides an electromagnetic fuel injector that is not beset by difficulties such as those that have just been described. The invention contemplates that the splitting and metering functions be contemporaneously performed by a flat thin disc orifice member located at the tip end of the injector. This thin disc orifice member can be easily manufactured with a suitable degree of precision. Direction of the split and metered parallel fuel flows is accomplished by a flow director member that is also at the injector tip, just downstream of the thin disc orifice member. The flow director member has holes arranged such that the flow from each orifice of the thin disc orifice member is directed off a wall portion of a corresponding flow director hole without the flow director holes altering the metering of the fuel. In other words, the flow director member performs only a direction function that directs the incoming parallel flows from the thin disc orifice member to outgoing flows that diverge at a desired included angle. The injector of the invention performs consistently well under both static (always flowing) and dynamic (on/off cycling) operations without degrading the spray angle. The injector of the invention has the further advantage of allowing the splitting, metering and directing functions to be relatively economically incorporated. For example, it is contemplated that the flow director member can be fabricated from a structural (high modulus of elasticity) plastic that can be injection molded.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention in accordance with the best mode contemplated at the present time for carrying out the invention.